Walter I, of the House of Grenier, was the lord of Caesarea in the Kingdom of Jerusalem from the 1120s until his death in the early 1150s. He clashed with his stepfather, Count Hugh II of Jaffa, over the lordship of Sidon, leading to a dramatic public accusation that Hugh intended to assassinate King Fulk. Walter in the end never received Sidon and spent his last years heavily indebted and marginalized.